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Thyroid

Reverse T3

Reverse T3 is an inactive thyroid hormone that may increase during stress, illness, or hormonal shifts. For women, elevated levels might influence menstrual regularity, energy, and fertility. Some providers consider it when evaluating unexplained cycle disturbances.

Doctor's Assessment Included

Reference Ranges

Female
pmol/l
Low 0.14 Normal 0.54 High

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Check your own value

What It Measures

This test measures the level of reverse triiodothyronine (rT3) in your blood. Reverse T3 is produced when the body converts T4 into an inactive form instead of active T3. It may serve as an indicator of how your body is prioritising thyroid hormone utilisation.

Why It Matters

For women, elevated Reverse T3 may suggest the body is under stress, which can potentially affect hormonal balance, ovulation, and cycle regularity. Some healthcare providers consider this marker when evaluating fertility concerns alongside other thyroid values.

When to Test

Some people may consider testing Reverse T3 when experiencing persistent fatigue or symptoms of low thyroid function despite normal TSH and T4 levels. It might be useful during periods of chronic stress or illness. Your healthcare provider can advise on whether this test is appropriate.

Symptoms

Low Levels

Low Reverse T3 levels are less commonly discussed, but some healthcare providers note that very low levels may occasionally be seen alongside hyperthyroid states. Symptoms might overlap with those of an overactive thyroid. Discuss any concerns with your healthcare provider.

High Levels

Some people with elevated Reverse T3 levels may experience fatigue, brain fog, weight gain, or cold intolerance despite normal T4 and TSH readings. High levels might suggest the body is under significant physiological stress. Your healthcare provider can help interpret these results.

Recommendations

Female

If Low

Low reverse T3 is generally not concerning.

If High

Elevated reverse T3 may indicate stress, illness, or a conversion issue. Consider investigating underlying causes.

Lifestyle Tips

Some people may help support healthy Reverse T3 levels by managing chronic stress, avoiding extreme caloric restriction, and prioritising sleep. Adequate nutrition with sufficient iron and selenium might also play a role. Always consult your healthcare provider before making changes.

Frequently Asked Questions

What causes Reverse T3 to become elevated?
Elevated Reverse T3 may result from chronic stress, severe illness, caloric restriction, or inflammation. Some healthcare providers suggest the body produces more Reverse T3 as a protective mechanism to slow metabolism during challenging periods.
Is Reverse T3 testing routinely recommended?
Reverse T3 is not typically part of standard thyroid panels. It is sometimes ordered when a healthcare provider suspects a conversion issue or when symptoms persist despite normal TSH and Free T4 levels. Your provider can determine if it is appropriate for you.
Can dieting increase Reverse T3 levels?
Some research suggests that significant caloric restriction or prolonged dieting may increase Reverse T3 levels as the body attempts to conserve energy. This is sometimes referred to as adaptive thermogenesis. Discuss dietary concerns with your healthcare provider.

Tests with related values

These panels measure values from the same category as this marker.

Fertility & Pregnancy

IVF Blood Test Complete (Women)

Everything in the IVF panel plus full thyroid, preconception nutrients, progesterone and CMV immunity.

TSH (Thyroid Stimulating Hormone) Prolactin AMH (Anti-Müllerian Hormone) Estradiol (E2) FSH (Follicle Stimulating Hormone) LH (Luteinizing Hormone) Free T4 (Thyroxine) Folate (Folic Acid) Vitamin B12 Ferritin Progesterone Vitamin D (25-OH) Chlamydia IgG HIV 1/2 Antibody + p24 Antigen Syphilis Screening Blood Type + Rh TPO Antibodies CMV IgG Hepatitis B Core Antibody Hepatitis B Surface Antigen Hepatitis C Antibody Rubella IgG Toxoplasmosis IgG Varicella Zoster D-Dimer Basic Blood Count
€495,-

Reverse T3

€130,-